Biology  5/e   Raven/Johnson
	Student   Online Learning Center

Hydrophobic interactions: Nonpolar molecules tend to bond or clump together in water solutions because the polar water molecules form hydrogen bonds among themselves and exclude or push aside the nonpolar molecules. This forcing together of nonpolar molecules contributes to the shapes of biologically important molecules such as phospholipids and proteins.

Reduced carbon compounds: Carbon has an atomic number of 6 and has four electrons in its outer energy level. It thus tends to form covalent bonds with other atoms so that four pairs of electrons are shared and its outer energy level is filled. As the carbon gains these shared electrons, it is reduced. Organic molecules, the molecules of living organisms, are built by carbon bonding to other atoms, especially hydrogen, oxygen, and other carbon.

Covalent bonds: In a covalent bond, electrons are shared between two atoms. Carbon, the backbone of all organic molecules, forms four covalent bonds. Covalent bonds represent stored energy. Forming a molecule with covalent bonds is a way of storing energy; breaking covalent bonds is a way of releasing energy that can be used to perform work. Covalent bonds are strong enough that they do not break easily, and thus organisms don't fall apart spontaneously.

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com.